The family and I went to see National Treasure: Book of Secrets last night. In one scene, four people are trapped on a square platform that sits balanced on it's center point. When anyone moved, the weight shifted and the platform tilted (putting our heroes in peril, of course!). The characters were forced to quickly work out an arrangement for moving on the platform, working in conjunction with each other to keep it balanced. While the rest of the theater held its breath waiting for someone to fall, I just kept thinking what a great instant challenge that platform would make!
If you've seen this movie, you'll know what I'm talking about; if not, watch for it and join me in figuring out a way to adapt this idea to work with kids!